Fiber Distributed Data Interface

Backbone of the Future

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FDDI History

FDDI was developed by the American National Standards Institute (ANSI) X3T9.5 standards committee in the mid-1980's.  It is also an ISO standard, series 9314.  It was developed due to high-speed engineering workstations taxing the bandwidth on existing LANs using either ethernet or token ring.  Network reliability had also become an increasingly important issue as mission-critical applications were moved from large computers onto networks.

Today, an extension of FDDI called FDDI-2 supports voice and video transmission as well as data.  Also, FDDI Full Duplex Technology, or FFDT is available, using the same network setup as FDDI but with twice the bandwidth, at 200 Mbps.

FDDI Transmission

FDDI data is transmitted on two types of fiber optic lines: single-mode and multi-mode.  A mode is a light ray that goes through the fiber, usually either from a laser or other light-generating device.

A single-mode setup only allows one mode of light to go through the fiber.  This method achieves higher performance connectivity over much larger distances, so it is used most often between buildings and across geographically dispersed environments.

A multi-mode fiber allows more than one light ray, which limits the bandwidth.  This makes it the ideal technology for connectivity within a single building or in a relatively small geographic environment.